1. Technical Field
The present invention relates generally to technology for providing a composite image based on optical transparency, and more particularly to a method for providing a composite image based on optical transparency, in which, using a light and small device like eyeglasses, a virtual image that fills a user's field of view may be provided along with see-through vision to the real world without blocking a view of an external environment, and an apparatus for the same.
2. Description of the Related Art
Generally, 3D display techniques are largely categorized into the following three types. The first one is a method for artificially implementing a natural phenomenon in which light emitted from a light source (e.g. the sun) is reflected from a surface having a certain shape, and the reflected light, having a specific wavelength (color), is directed to the eyes of an observer, for example, like an ideal holographic display. The second one is a method for generating and displaying two images that artificially implement binocular disparity, which is the difference between images input to the left and right eyes, among the characteristics of human visual 3D recognition. The final one is a method for implementing an effect similar to the effect of the first method by delivering multiple viewpoints to the user's eyes based on the second method.
As described above, the conventional methods for implementing 3D stereoscopic images may not realize an optical see-through capability, which enables users to freely see their surroundings as though looking through eyeglasses.
Most lightweight Head Mounted Displays (HMDs) for supporting an optical see-through capability, introduced for customers in the market, have a narrow viewing angle that ranges from about 30 to 40 degrees. According to a case study report, the maximum viewing angle of an optical see-through wearable display having an external form as light as eyeglasses is only 56 degrees, as described in the thesis titled “Wearable display for visualization of 3D objects at your fingertips” (written by Ungyeon Yang and Ki-Hong Kim and published in SIGGRAPH' 14 ACM SIGGRAPH 2014 Posters).
Also, like the iOptik system developed by INNOVEGA, the method of placing a high-resolution micromini display panel very close to the eyes has been proposed as a method for implementing a wearable display as light as eyeglasses, but this method is problematic in that it is inconvenient because a user must wear a special contact lens.
Also, as proposed in a thesis titled “Pinlight displays: wide field of view augmented reality eyeglasses using defocused point light sources” (written by Andrew Maimone, Douglas Lanman, Kishore Rathinavel, Kurtis Keller, David Luebke, and Henry Fuchs and published in ACM Transactions on Graphics (TOG)—Proceedings of ACM SIGGRAPH 2014 TOG Homepage archive, Volume 33 Issue 4), the existing method for implementing a display in the form of light eyeglasses is not satisfactory for use in commercial products for customers because of multiple disadvantages, such as nonuniformity of a light source of a backlight panel configured with point light sources, low quality of a provided image due to an incomplete eye-tracking function, and the like.
According to the conventional method, a panel for creating multiple point light sources called “pinlights” is formed by etching patterns at regular distances (by cutting grooves using a robot arm of a 3D printer) on an acrylic sheet, and a backlight panel is implemented in such a way that, when light incident from edge-lit LEDs meets an etched divot while travelling after being totally internally reflected, the light is emitted outside the acrylic sheet via the point-type light. That is, the conventional method employs some backlight implementation methods commonly used in the technical field for implementing a flat display panel, for example, an edge-lit screen, a lightguide, and the like.
Therefore, the conventional method is disadvantageous in that it is difficult to implement point light sources having equal brightness (the same amount of light) at all positions in a pinlight panel. Also, respective light rays emitted by multiple point light sources may have different brightness and wavelengths. When a display panel for a TV is manufactured, the corresponding problem may be solved by additionally applying a diffusion film for evenly diffusing light in between the front point light source unit and a color pixel panel (e.g., an RGB panel). However, this method is merely for acquiring the effect of evenly emitting light from all parts of a flat panel, but is not suitable for an optical see-through wearable display because transparency (a see-through effect) for penetrating a real (virtual) image outside the image panel is obstructed. In connection with this, Korean Patent Application Publication No. 10-2015-0026455 discloses a technology related to “Apparatus and method for designing display for user interaction in the near-body space”.